The invention deals with a chucking means or tool unit which fits into a co-axially rotating spindle that has a conical bore co-axial to the rotational axis of the spindle. The tool unit is to be inserted into the conical bore of the spindle and firmly secured therein.
Such tool units have been known in tool machinery for a long time. They hold chucking cones whose conal angles either are inside or outside. In the first case, e.g., in so-called Morse tapers, it is sufficient to insert the tool with its conical end into the corresponding inner conical surface of the spindle in order to achieve a precise and tight connection. To achieve disconnection, special loosening tools are needed, such as wedges that have to be pushed in laterally. In other cases, and generally speaking, whenever vertical wedges are used, the tightening of a conal connection is achieved by means of tightening screws.
U.S. Pat. No. 3,651,739 issued Mar. 28, 1972 to Wolf shows an example of this kind of chucking device wherein the tool unit has an axial backward neck for accepting the cone connection. To take out the spindle laterally, it is provided with a box that has a number of slots in various places which correspond to the tongues of the indentations of the tool unit. These boxes also have indentations on the outside which fit into the box when pulled in laterally. The tongues of the boxes are thus pressed inside and catch the indentations of the tongue behind the neck of the unit in order to grasp it, to pull it into the lateral opening, and to tighten it inside.
The invention also deals particularly with chucking devices for special tool units, namely the so-called high frequency spindles. These spindles are small machines which have high-speed motors, are highly precise, and they usually are used as grinding, cutting, or drilling units. Basically, they have cylindrical housings of about 40 to 80 mm circumference. Oftentimes several such spindles are put together in one machine, thus forming drilling machines, e.g., for the purpose of drilling sheet bars in the clock industry or for drilling printed circuit boards.
Because of the smallness of these units, the chucking of the tools presents difficulties. Self-retarding cone connections do not stay together because of the small size of these cones. This is even the case when an additional screw attachment is considered for use. The activation of such a screw attachment requires more time during which the unit or even a larger number of units combined in one machine can not continue to function. Therefore, attempts have been made, following a suggestion which had not directly to do with this particular technique, to utilize a polygonal turning shaft at one end of the tool unit; this shaft was to correspond to an inner polygonal turning bore inside the spindle to assure reliability. This method works as long as the tools are put in manually, and as long as the exact position can be detected by checking, so that the corners of the polygonal turning shafts do not get into each other's way and can get inserted this way.
The trend in working with such machines using high frequency spindles is, however, to automate the tool change as much as possible. Such a tool change can be a necessity not only in regard to the tools' wear, but also in cases where, e.g., a machine has to deliver drillings of various diameter sizes. It is desirable in these cases that the machine first completes the drillings of one kind, then is taken to the tool magazine where the tools are changed automatically, and then continues the other drillings with the new tools.
The change of tools is done by dropping the spindle, taking out the tool unit, and grasping the new tool unit from above. In the automatic execution of these steps, it often happens that difficulties arise in connection with the putting together of the polygonal turning shafts, for example, when the shafts are misaligned and can not be brought together.